1. Field of the Invention
This invention relates generally to an air and water supply valve structure in an endoscope. More particularly, this invention relates to an air and water supply valve structure for alternatively supplying air or water into a body cavity or the like, in an endoscope for medical use.
2. Description of Related Art
An air and water supply valve structure is provided at a manual operation part of an endoscope for medical use. If an operator operates the air and water supply valve with fingers, air or water is alternatively supplied into a body cavity.
A conventional air and water supply valve structure comprises a cylinder, a piston and operation members such as buttons. The cylinder is fixed at a predetermined position of the manual operation part, and the piston is slidably inserted into the cylinder. An air supply button is attached to the top of the piston. If the operator closes an air leak opening of the air supply button, the air in the cylinder is supplied into the body cavity through an air supply tube. If the piston is pressed down by operating a water supply button, the supply of the air is stopped and the water in the cylinder is supplied into the body cavity through a water supply tube.
The conventional air and water supply valve structure has a check valve on the air supply tube. The check valve prevents a liquid in the body cavity from flowing back into the cylinder through the air supply tube, and thus prevents the liquid from contaminating the cylinder and the like. In the conventional air and water supply valve structure, however, the resistance of the check valve on the air supply tube increases a pressure loss in the air supply, and this necessitates, an air source that is able to overcome the resistance. This substantially increases the consumption of energy. Moreover, in the conventional air and water supply valve, the check valve makes it difficult to clean the air supply tube.
The cylinder and the piston have circular openings connected to air supply passages. When the positions of the openings are matched to one another, the air supply passages are connected to one another through the openings to supply the air. If the piston is slid to bring the openings out of line, the air supply passages are disconnected and the supply of the air is stopped.
The conventional valve structure, however, cannot achieve the satisfactory airtightness of the valve when the air supply passage is blocked. In order to improve the airtightness of the conventional structure, the openings must be much brought out of line, and the stroke length of the piston must be a large amount. If the stroke length of the piston is designed to be large, however, an operator must deeply press the air supply button and this makes it difficult to operate the valve. For this reason, it is unpreferable to increase the stroke length of the piston, and thus, the conventional valve structure cannot improve the airtightness of the valve.
It is therefore an object of the present invention to provide an air and water supply valve structure in an endoscope that functions as a check valve without a special check valve and reduces a pressure loss in air supply to the minimum. Another object of the present invention is to provide a valve structure, which improves the airtightness of the valve without increasing the stroke length of a piston.
In view of the foregoing, it is an object of the present invention to provide an air and water supply valve structure provided at a manual operation part of an endoscope, comprising: a base cylinder that is a hollow cylinder connecting: to an air feed tube feeding air into the base cylinder, to a water feed tube feeding water into the base cylinder, to an air supply tube to supply the air from the base cylinder to an air and water supply opening formed at an end of an insertion part of the endoscope, and to a water supply tube to supply the water from the base cylinder to the air and water supply opening; a first piston that is a hollow cylinder slidably inserted into the base cylinder, the first piston having a connection opening to connect the air feed tube and an inner space of the first piston, the first piston having a connection passage to connect the water feed tube and the water supply tube; a second piston that is a hollow cylinder arranged inside the first piston, an inner space of the second piston being connected to the air supply tube; a first operation member provided to the second piston, the first operation member being pressed by first and second steps, the first operation member connecting, when pressed by the first step, the inner space of the first piston and the inner space of the second piston, and the first operation member disconnecting, when not pressed, the inner space of the first piston and the inner space of the second piston; and a second operation member provided to the first piston, wherein when the first operation member is pressed by the second step, the second operation member is pressed and positions the first piston such that the connection opening of the first piston is disconnected from the air feed tube and that the connection passage of the first piston connects the water feed tube and the water supply tube.
According to the present invention, if the first operation member is pressed by the first step, the inner space of the first piston connects to the inner space of the second piston, and thus, the air fed into the inner space of the first piston is supplied to the air supply tube through the inner space of the second piston. Consequently, the air is supplied into the body cavity.
If the first operation member is pressed by the second step, the second operation member operated by this operation positions the first piston at such a position that the connection opening of the first piston can be withdrawn from the air feed tube, and this stops the supply of the air and that the connection passage of the first piston can connect the water feed tube and the water supply tube. Consequently, the water is supplied into the body cavity. The air is switched to the water in this manner. In short, if the connection opening of the first piston is withdrawn from the air feed tube, the air is supplied from the air feed tube to a water tank. This raises the inner pressure of the water tank, so that the water is supplied from the water tank into the water feed tube.
When the air is supplied by pressing the first operation member by the first step, the inner pressure of the air supply tube is higher than that of the body cavity. For this reason, the liquid in the body cavity never flows back into the air and water supply valve through the air supply tube. If, however, the inner pressure of the body cavity is higher than the inner pressure of the air supply tube when the first operation member is not operated, the backflow flows into the inner space of the second piston through the air supply tube. At this time, however, the inner space of the first piston and the inner space of. the second piston are unconnected since the first operation member is not operated. Thus, the backflow never flows into the inner space of the first piston, and does not contaminate the first piston and the base cylinder. In short, the air and water supply valve structure of the present invention has the first operation member functioning as a check valve, and this eliminates the necessity of a special check valve and reduces the pressure loss in the air supply to the minimum.
If a button is used in the first operation member, the inner space of the first piston and the inner space of the second piston are connected through a connection opening formed in the button when the button is pressed by the first step. Therefore, the air can flow smoothly without any resistance to the air supply tube, and this reduces the pressure loss in the air supply to the minimum.
If an elastic member is used in the first operation member, a cut groove formed in the elastic member is opened when the elastic member is squashed. Consequently, the inner space of the first piston is connected to the inner space of the second piston through the open cut groove. Therefore, the air can flow smoothly without any resistance to the air supply tube, and this reduces the pressure loss in the air supply to the minimum.
If a spiral spring whose adjacent spirals are in close contact with one another is used in the first operation member, the inner space of the first piston and the inner space of the second piston are connected through gaps formed between the spirals when the spiral spring is buckled. Therefore, the air flows into the air supply tube without any resistance, and this reduces the pressure loss in the air supply to the minimum.
If a shutter plate is used in the first operation member, an opening for connecting the inner space of the first piston and the inner space of the second piston is opened when a pressing member presses the shutter plate against the force of a forcing member. Consequently, the inner spaces of the first and second pistons are connected. Therefore, the air can flow smoothly without any resistance to the air supply tube, and this reduces the pressure loss in the air supply to the minimum.
Preferably, the air supply tube and the water supply tube are straight over predetermined lengths, respectively, so that a cleaning brush can easily be inserted into them. Thus, the air supply tube and the water supply tube can be cleaned easily. More preferably, the air supply tube is straight and arranged parallel to an axial direction of the base cylinder over a predetermined length and has a mouth thereof within an inner diameter of the base cylinder, so that the cleaning brush can easily be inserted from cylinder into the air supply tube. Thus, the air supply tube can be cleaned easily.
To achieve the above mentioned object, the present invention provides a valve structure in an endoscope, comprising: a first member having a first passage for a fluid, the first passage having a first opening; and a second member having a second passage for the fluid, the second passage having a second opening; wherein the first and second members are slidable with respect to one another in a sliding direction, the first and second passages are connected through the first and second openings when the first and second openings are faced to one another, the first and second passages are disconnected when the first and second openings are not faced to one another, and at least one of the first and second openings has a length thereof in the sliding direction being shorter than a length thereof in a direction perpendicular to the sliding direction.
According to the present invention, the opening of at least one of the two slidable members of the valve has a shorter side in the sliding direction and has a longer side in the direction perpendicular to the sliding direction. For example, the opening is an oblong with a longer side in the sliding direction and a shorter side in the perpendicular direction, or an oval with a shorter diameter in the sliding direction and a longer diameter in the perpendicular direction. Therefore, the length in the sliding direction can be reduced without reducing an opening area, more specifically a fluid passage area. This increases an interval between the openings out of line. It is therefore possible to improve, without changing the stroke length of the piston, the airtightness of the valve when the passages are unconnected.